Changed plant resource mass determination to only calculate for the s…

…pecific cell.

virtual_rainforest/models/animals/plant_resources.py

@@ -31,7 +31,7 @@ def __init__(self, data: Data, cell_id: int) -> None:
         self.data = data
         """A reference to the core data object."""
         self.mass_current: float = (
-            data["layer_leaf_mass"].sum(dim="layers").to_numpy()[cell_id]
+            data["layer_leaf_mass"].sel(cell_id=cell_id).sum(dim="layers").item()
         )
         """The mass of the plant leaf mass [kg]."""